Utilization of radio resources and channels is continuously subject to much research and development in order to optimize system throughput due to the limited availability of radio resources in communications systems. This is especially true when introducing new communications services to the existing communications systems. An example of such a new communications service is Multimedia Broadcast Multicast Service (MBMS). The benefit of this MBMS service is that it enables simultaneous distribution of data to several users using the same physical channel, i.e. so-called point-to-multipoint transmission. For more information of MBMS reference is made to the 3GPP document [1].
However, although the existing communications systems, e.g. GSM (Global System for Mobile communications) and EDGE (Enhanced Data rates for GSM Evolution) communications systems, are typically dimensioned for providing guaranteed minimum C/I (carrier-to-interference) levels adapted for traditional voice services, these guaranteed minimum C/I levels are often too low to successfully provide new high bit rate services, e.g. video streaming over MBMS. Due to the demand for high bit rates, these services must often use the maximum number of allowed communications resources (time slots).
However, radio link simulations have shown that even when using the maximum number of communications resources in GSM/EDGE systems, data blocks often have to be re-transmissions many times to provide acceptable robustness down to the minimum guaranteed C/I levels. The number of such re-transmission to provide the acceptable robustness is, though, often too high in existing GSM/EDGE systems, resulting in unacceptable low throughputs.
The obvious solution to this trade-off between low robustness (due to too few re-transmissions) and low throughput (due to too many re-transmissions) is to introduce a multi-carrier EDGE solution. However, although this is possibly relatively straightforward in the base stations of existing communications systems, a multi-carrier solution would require major changes in the mobile terminals because these terminals then have to process multiple channels simultaneously, both in analogue and digital parts.